An activist who entered a luxury shop to demonstrate against tax avoidance has had her criminal charges dropped after it was found she was carrying only 16 leaflets instead of 20 – the threshold for the criminal offence she was charged with.

Francesca Hyde, 28, spent 24 hours in a holding cell along with more than 150 members of campaigning group UK Uncut after protesting at the Fortnum & Mason food store in Piccadilly, London, during a TUC-organised march on 26 March 2011.

Hyde and 144 others, including minors, were subsequently charged with aggravated trespass but the Crown Prosecution Service (CPS) soon dropped charges against all but 30 demonstrators who they singled out as being more dangerous activists as they were carrying fliers, megaphones and beach balls.

Hyde was originally believed to have been in possession of more than 20 UK Uncut leaflets but, on the second day of her trial at Westminster magistrates court last week, it was discovered that a number of leaflets contained in her evidence bag were from the TUC or were theatre tickets stubs that had been wrongly logged as UK Uncut material. When her defence lawyer raised the matter, prosecution lawyers reviewed her case and informed her that she no longer face trial.

On Tuesday afternoon, a judge found nine of Hyde's fellow defendants guilty of aggravated trespass with intent to intimidate and sentenced them to a one-year conditional discharge plus costs. A previous trial of 10 Uncut activists in November also returned guilty verdicts.

The trial served as the first test of the director of public prosecutions' new guidelines on protest, which were issued to help prosecutors clarify the difference between peaceful protesters and those intent on acts of public disorder.

Lawyers acting for UK Uncut defendants asked the CPS to look again at the defendants who had been charged in light of the new guidelines which seek to distinguish between those "intent on violence and disruption" and those who "attend protests and demonstrations with an essentially peaceful purpose but who may cross the line".

Responding to a request for immediate review, CPS senior lawyer Edmund Hall said: "The Crown case is put on the basis that their individual actions, or the property they were in possession of, puts them firmly in the category of taking a leading role in the protest and additionally thereby encouraging other protestors, whose cumulative effect was to intimidate [Fortnum & Mason] staff and customers."

Hyde said the dropping of the charges highlighted "the whole ridiculous nature" of the case.

"I don't understand why people are going to court for having information on them and the fact that I had four less of those leaflets, I don't understand why that should make a huge difference [to me] being prosecuted or not," she said. "I lose four leaflets and I'm seen as 'peaceful'."

A CPS spokesperson said the decision to discontinue Hyde's case had been "entirely case-specific and sets no precedent for any other case," adding: "During the trial, the prosecutor re-reviewed the case and decided that information provided at court had tipped the balance and meant that it was no longer in the public interest to proceed."

Speaking about the other defendants, the CPS said it was satisfied that it was in the public interest to prosecute these individuals and had been vindicated by Tuesday's guilty verdicts.

The CPS said: "The right to protest is an important one and our policy is to consider extremely carefully whether it is in the public interest to prosecute protesters. This is reflected in our decision to continue the prosecution of only 29 of the 145 people originally charged by the police.

The district judge said: "The precious right to demonstrate, which needs to be jealously guarded, does not extend to a right to engage in a mass incursion into, and occupation of, a shop which will inevitably disrupt its retail business.'"